The invention relates to a reflector lamp comprising
a reflector body of vitreous material having a longitudinal axis, a basal portion, a rim which defines a light-emitting opening of said reflector body, and an inner reflector surface which extends from the basal portion to the rim of the reflector, PA1 a lens of vitreous material fused to said rim, PA1 a light source arranged within said reflector body, and PA1 a reflective coating on said inner reflector surface. PA1 the reflective coating comprises a first reflective coating portion extending from said rim towards said basal portion and a second reflective coating portion which extends from an axial position spaced from said rim to said basal portion, and the second reflective coating portion consists essentially of silver and the first reflective coating portion consists essentially of a material other than silver.
Such a lamp is well known in the lighting industry and includes, for example, Parabolic Aluminized Reflector (PAR) lamps. In PAR lamps the reflective coating consists of aluminum and the light source is typically an incandescent filament or halogen capsule. The lens and the reflector body are typically a borosilicate hard glass and are fused to each other using a flame sealing process. As used herein, `fused` refers to a sealed joint between the reflector body and the lens in which the vitreous material of each part is fused to the other by a high temperature process such as flame sealing, and excludes, for example, a joint where the two parts are bonded together with an adhesive, such as epoxy.
As part of a worldwide movement towards more energy efficient lighting, recent government legislation in the United States (commonly referred to as the national Energy Policy Act "EPACT") has mandated lamp efficacy values for many types of commonly used lamps including parabolic aluminized reflector (PAR) lamps. These minimum efficacy values will become effective in 1995 and only products meeting these efficacy levels will be allowed to be sold in the United States. The efficacy values for PAR-38 incandescent lamps have been established for various wattage ranges. For example, lamps of 51-66 W must achieve 11 lumens per Watt (LPW), lamps of 67-85 W must achieve 12.5 LPW, lamps of 86-115 W must achieve 14 LPW and lamps in the range 116-155 W must achieve 14.5 LPW.
PAR 38 lamps currently on the market with a reflective coating of aluminum and an incandescent filament have efficacies which will fail to meet the EPACT minimum efficacy standards. For example, the typical 150 W PAR 38 lamp provides only about 10-12 LPW (initial) and a 2000 hour life. It is possible to design a filament for a conventional aluminized reflector body which would meet the EPACT standards. However, such a filament would result in a greatly reduced lamp life (on the order of, for example, 800-1200 hours) which would not be commercially acceptable in view of the 1800-2000 hour lamp lives now available in conventional PAR lamps.